The present invention relates to fastener structures having hook elements which are adapted to engage with engaging material such as loop elements. Fasteners formed from such structures are useful in many applications and particularly applications which require permanent or semi-permanent fastening.
Hook and engagement material fasteners typically include hook elements that engage with a loop material or other engagement material. The hook structure of the fastener engages the engagement material to fasten the two items together, while also assuring release from the engagement material in a desired manner. Many hook fastener structures are made of cut monofilaments which can elongate during fastener separation to release the engagement material, so that they must feature excellent tensile and bending strength over repeated cycles of fastening and unfastening. Such fasteners are useful in apparel, for example, where fastening must be secure, release must be relatively trouble free and multiple cycles of fastening and washing can be expected over the life of a garment. Monofilament hooks can be spaced densely according to textile weave, thus causing very reliable fastening and durability in repeated use. However, these thin monofilament hooks can be expensive to manufacture, and are typically less suitable where great fastening strength (force per unit area of fastener required to separate the hook portion of the fastener from the engagement material), is required.
Other hook fastener structures are manufactured by being integrally molded using, for example, continuous or other injection molding. These hook portions are typically more rigid than the monofilament type hooks in order to increase fastening strength. However, such rigidity can cause failure over repeated cycles of fastening and release, so that such fasteners are typically better suited for semi-permanent or permanent applications where multiple releases are not required but fastening strength is required, such as installation of signage or automotive applications including installation of seat fabric, seat covers and other interior finish materials.
One challenge faced by manufacturers of hook and loop fastener material for semi-permanent applications is to develop a configuration that allows the hook structure to engage the engagement material with great fastening strength, but yet feature sufficient flexibility to permit sufficient temporary bending at the curved portion to allow engagement of the loop portion of the fastener to occur during fastening. One approach has been to include additional material in the stem of the hook portion, such as by adding lateral or other dimensional thickness, in order to impart additional strength to the stem, while allowing the curved portion of the hook which engages the loop to be thinner or of less material in order to bend and retain sufficient resilience to engage the loop material. The stiffer stems of such hooks can impart additional support and strength to the curved portions in order to give the fastener considerable fastening strength. Yet in such designs, the stem portions need to be sufficiently long to cause the curved portions to penetrate sufficiently deeply into the loop material to achieve proper semi-permanent or permanent, strong engagement with the hook portion.
One example of a conventional design is described in U.S. Pat. No. 5,131,119, which is incorporated by reference. That patent discloses rows of hooks that feature reinforcing ribs that extend partially the length of the stem. A drawing of such a design from that patent constitutes FIG. 4 herein. Another example is described in U.S. Pat. No. 5,339,499, which is also incorporated by reference, and which discloses hooks with stems that feature a substantially greater lateral thickness than the crook portions. Drawings from that Patent which constitute FIGS. 5A, 5B and 5C herein show such a stem with such a greater thickness. U.S. Ser. No. 11/043,339 filed Jan. 26, 2005 in the name of Akeno, et. al, published as U.S Pub. No. 2005/0160534 A1 on Jul. 28, 1995, which is also incorporated herein by reference, discloses molded hook fastener structures with hooks that have lateral reinforcement, and continuous manufacturing processes for making them.